Kojiro Nakao

Preserving Normal Ventricular Activation Versus Atrioventricular Delay Optimization During Pacing: The Role of Intrinsic Atrioventricular Conduction and Pacing Rate

The purpose of the study was to compare the effects of DDD pacing with optimal AV delay and AAI pacing on the systolic and diastolic performance at rest in patients with prolonged intrinsic AV conduction (first‐degree AV block). We studied 17 patients (8 men, aged 69 ± 9 years) with dual chamber pacemakers implanted for sick sinus syndrome in 15 patients and paroxysmal high degree AV block in 2 patients. Aortic flow and mitral flow were evaluated using Doppler echocardiography. Study protocol included the determination of the optimal A V delay in the DDD mode and comparison between AAI and DDD with optimal A V delay for pacing rate 70/min and 90/min. Stimulus‐R interval during AAI (AHI) was 282 ± 68 ms for rate 70/min and 330 ± 98 ms for rate 90/min (P < 0.01). The optimal A V delay was 159 ± 22 ms, A V delay optimization resulted in an increase of an aortic flow time velocity integral (AFTVI) of 16%± 9%. At rate 70/min the patients with ARI ≤ 270 ms had higher AFTVI in AAI than in DDD (0.214 ± 0.05 m vs 0.196 ± 0.05 m, P < 0.01), while the patients with ARI > 270 ms demonstrated greater AFTVI under DDD compared to AAI(0.192 ± 0.03 m vs 0.166 ± 0.02 m, P < 0.01). At rate 90/min AFTVI was higher during DDD than AAI (0.183 ± 0.03 m vs 0.162 ± 0.03 m, P < 0.01). Mitral flow time velocity integral (MFTVI) at rate 70/min was higher in DDD than in AAI (0.189 ± 0.05 m vs 0.173 ± 0.05 mP < 0.01), while at rate 90/min the difference was not significant in favor of DDD (0.149 ± 0.05 m vs 0.158 ± 0.04 m). The results suggest that in patients with first‐degree AV block the relative impact of DDD and AAI pacing modes on the systolic performance depends on the intrinsic AV conduction time and on pacing rate.

Electrophysiological abnormalities of the atrial muscle in patients with paroxysmal atrial fibrillation associated with hyperthyroidism.

objective Atrial fibrillation (AF) is common in patients with hyperthyroidism. Although the choice of an antiarrhythmic agent should be based on its electrophysiological effects and the electrophysiological properties of the arrhythmia in question, the atrial electrophysiological features of AF associated with hyperthyroidism are unknown. The purposes of this study are to clarify the atrial electrophysiological abnormalities of AF with hyperthyroidism, and to propose effective therapies for AF in patients with hyperthyroidism.

Extended Distribution of Prolonged and Fractionated Right Atrial Electrograms Predicts Development of Chronic Atrial Fibrillation in Patients with Idiopathic Paroxysmal Atrial Fibrillation

Prolonged and Fractionated RA Electrogram in PAF Folio. Introduction: This study evaluates whether electrophysiologic abnormalities in patients with idiopathic paroxysmal atrial fibrillation (PAF) predict the transition to chronic atrial fibrillation (CAF).

The Influence of β‐Adrenergic Agonists and Antagonists on T‐Wave Alternans in Patients with and Without Ventricular Tachyarrhythmia

Background: T‐wave alternans (TWA) is an important noninvasive measurement of ventricular tachyarrhythmia (VT) and is known to be influenced by the sympathetic nervous system. We examined the correlation between TWA measurement and the sympathetic nervous system in patients with and without VT.

Ventricular Fibrillation in a Patient with Prominent J Wave in the Inferior and Lateral Electrocardiographic Leads After Gastrostomy

We describe the case of a 39‐year‐old man who experienced a ventricular fibrillation storm related to a prominent J wave in the inferior and lateral electrocardiographic leads on the day after gastrostomy. The J wave slowly decreased after amiodarone therapy (400 mg/day) was started, and ventricular fibrillation disappeared.

A Patient with LQTS in Whom Verapamil Administration and Permanent Pacemaker Implantation Were Useful for Preventing Torsade de Pointes

A 21‐year‐old woman with long QT syndrome and missense mutation in HERG (T613M), suffered from repeated attacks of pause dependent torsade de pointes, even though she was given β‐blockers and underwent stellate ganglion block twice at the age of eight. After she received permanent pacemaker implantation and administration of verapamil, no premature beats or pause dependent torsade de pointes was observed. (PACE 2004; 27:123–124)

Effects of Intravenous Nifekalant, A Class III Antiarrhythmic Drug, on Atrial Vulnerability Parameters in Patients with Paroxysmal Atrial Fibrillation

Nifekalant, a class III antiarrhythmic drug, has been shown to suppress ventricular tachyarrhythmias, but its effects on AF are unclear. The aim of this study was to clarify the effects of nifekalant on the atrial vulnerability parameters in patients with paroxysmal AF. The study included 18 patients with paroxysmal AF who underwent electrophysiological study before and after intravenous infusion of nifekalant. The atrial electrophysiological parameters including the atrial effective refractory period (AERP), maximum intraatrial conduction delay, and wavelength index, calculated as the ratio of AERP to the maximum conduction delay, were quantitatively measured at baseline and during nifekalant infusion. The mean AERP was significantly prolonged from 214 ± 27 ms at baseline to 242 ± 39 ms after nifekalant (P < 0.001). Although earlier studies have shown that nifekalant does not affect the atrial conduction time, the mean maximum conduction delay of the study patients was significantly prolonged from 59 ± 19 ms at baseline to 72 ± 28 ms after nifekalant (P = 0.015). There was no significant difference in the wavelength index at baseline (4.1 ± 1.7) and after nifekalant (4.1 ± 2.5). However, when the differences of AERP and wavelength index were defined as each parameter during nifekalant infusion minus that at baseline, the difference of AERP showed a direct positive correlation with that of the wavelength index (P = 0.013). In conclusion, nifekalant may be effective in the prevention of AF due to prolongation of the AERP. However, in those patients who have a lesser degree of prolongation of the AERP by nifekalant, the wavelength index tended to be decreased, suggesting that the drug might augment the propensity for AF. (PACE 2004; 27:212–217)

Simultaneous atrial and ventricular pacing to facilitate mapping of concealed left-sided accessory pathways.

NAKAO, K., et al.: Simultaneous Atrial and Ventricular Pacing to Facilitate Mapping of Concealed Left‐Sided Accessory Pathways. Several local electrogram characteristics have been proposed as criteria to predict successful ablation. However, poor specificity due to obscuration of the retrograde atrial electrogram by the ventricular electrogram is problematic. The aim of this study was to analyze local electrograms obtained by simultaneous pacing to identify quantitative criteria that may predict successful ablation sites for concealed left free‐wall accessory pathways. Twenty‐four local electrograms from 10 successful and 14 unsuccessful ablation sites in ten patients were analyzed. Retrograde atrial electrograms were confirmed by the simultaneous pacing method. The intervals between the retrograde atrial electrogram of the coronary sinus and the ablation site, the initiation of the ventricular electrogram and the retrograde atrial electrogram, and the stimulus and retrograde atrial electrogram were analyzed. All retrograde atrial electrograms could be confirmed clearly by the simultaneous pacing method. The interval between the retrograde atrial electrogram of the coronary sinus and that of the ablation site was shorter at successful sites than at unsuccessful sites (‐7.0 ± 9.2 ms vs 5.7 ± 2.7 ms; 95% confidence interval, ‐18 to ‐7; P < 0.0001). An interval of ≤ 0 ms resulted in 100% sensitivity and 92.7% specificity for success. The other two interval measurements at successful sites did not differ significantly from those at unsuccessful sites. The authors propose an interval of ≤ 0 ms between the retrograde atrial electrogram of the coronary sinus and that of the ablation site confirmed by the simultaneous pacing method as a quantitative criterion to identify the successful ablation site for concealed left free‐wall accessory pathways. Application of this criterion may reduce the number of unnecessary ablations.

Prompt and Long-term Prophylactic Effect of Closed Loop Stimulation against Paroxysmal Atrial Fibrillation in a Patient with Sick Sinus Syndrome

A 72‐year‐old woman with sick sinus syndrome (SSS), who had frequent paroxysmal atrial fibrillations (PAfs) and normal cardiac function, was admitted to our hospital due to syncope. PAfs frequently occurred during the first week after DDD pacemaker implantation (PMI), with closed loop stimulation (CLS) rate‐adaptive mode off, but were completely suppressed during the second week, with CLS on, and had been well‐controlled over three years thereafter. However, PAfs occasionally occurred under intense sympathetic activity during 6 months after PMI as well, and were effectively terminated by disopyramide which had anticholinergic effect. Thus, the development and maintenance of PAf were thought to be associated with destabilized cardiac autonomic activities, that is, sympathetic and parasympathetic dominance, respectively. Additionally, heart rate variability analyses after implementation of CLS revealed the restoration of sympathetic and parasympathetic components. Accordingly, CLS mode was considered to play a critical role in preventing PAf by reflecting autonomic activity in heart rhythm in this SSS patient.

Angiotensin‐Converting Enzyme Inhibitor Suppresses the Incidence of Prolonged and Fractionated Right Atrial Electrograms

Introduction: Although prolonged and fractionated right atrial electrograms have been reported as predictors of the development of chronic atrial fibrillation in patients with paroxysmal atrial fibrillation (PAF), the effects of angiotensin‐converting enzyme inhibitor (ACEI) on these electrophysiologic abnormalities remain unknown. The purpose of this study was to evaluate whether ACEI influences these electrophysiologic abnormalities of atrial muscle in patients with PAF.